041: Structure-Properties Relationships of Whey Permeate Powders

Introduction

Whey permeates are byproducts of the dairy industry, generated through the ultrafiltration of whey produced during cheese manufacturing. They are nutritionally valuable due to their high concentrations of essential minerals and micronutrients. Although permeate powders are produced and marketed on a large scale, they are still mired with numerous stability issues, and the valorization of permeates in the form of powders remains challenging due to their physical instability. Therefore, this study aimed to understand the structure-properties relationships of the commercial whey permeate powders. In particular, the water plasticization effect on the whey permeate powders was investigated.

Methods

We proposed a novel two-phase model of permeate powders with two types of particle morphologies: (1) particles consisting of small lactose crystallites dispersed in a continuous amorphous phase consisting of lactose and all non-lactose constituents, and (2) particles consisting of one or a few large lactose crystals with a thin, discontinuous amorphous surface layer. The glass transition temperature of the whey permeate powders was identified by DSC and characterized in a very low-temperature range from 5 to 15°C at water activity (aw) between 0.18 and 0.22. Whey permeate powders were equilibrated in aw of 0.11 to 0.68. We then applied the Gordon-Taylor equation to model the Tg of the whey permeate powders as plasticized by the water.

Results

The results suggested a significant decrease of the Tg to -12, -35, and -21°C at aw = 0.43 with the water content of 2.7, 2.6, and 3.1% w/w (w.b.). for the permeate powders, indicating that they are fairly hygro-sensitivities during storage. As only the water in the amorphous fraction is capable of plasticizing the particle, this present study analyzed the water content in the two physical states: amorphous and crystalline, by a modified drying method.

Significance

Overall, this study critically contributes to a deeper understanding of the physical structure, water relations, and thermal properties of whey permeate powders and sets a stage for future research on the mechanism of caking of permeate powders during transport and storage.

Authors: Tsung-Yueh Benjamin Peng, Didem Sözeri Atik, Job Ubbink